The purpose of the Histopathology Facility is two-fold: to process research animal tissues for conventional and specialized histology, and to provide histopathological evaluation of the tissues through a team of trained pathologists. The Facility occupies about 630 sq., feet of floor surface, and is physically located in the Unit 3 of the NDI, within the Division of Pathology and Toxicology. Currently, the Facility is staffed with three pathologists and three histologists. From the six, only 1.75 are AHFCC supported. The Facilities organizations and functions are very similar to those of any histology laboratory in non-clinical laboratories, hospitals or medical research institutions, having all standard equipment for conventional and specialized histopathology. The major pieces of equipment include 2 tissue processors, an embedding center, 2 rotary microtomes, a cryostat, 3 microscopes and one Videoplan image analyzer. The equipment is in good or excellent working condition. As such the Facility is capable of processing tissues and preparing slides from intramural and extramural experimental laboratory animal studies and human specimens. Furthermore, the Facility is in compliance with non-clinical good laboratory practice (GLP) rules. The ability of the Facility to perform various established techniques, to adapt and refine existing methodology, and to develop new analytic procedures is of vital importance in correlating molecular events to cellular responses. Consequently, a diverse group of AHFCC investigators rely on histopathology to provide fundamental biological and histopathological data from a wide range of experimental objectives. During the last 5 year period, 61 papers, all originating from CCSG-supported programs, have been co-authored by pathologists and have been published in peer-reviewed journals. Among special immunohistochemical techniques used are BrdU,PCNA,Ki67,p53,GST- P,GS,COX1,COX2, VEGF, ER, PR, TUNEL, ISEL, intermediate filaments and cytoskeletal protein procedures. In general, any special known technique can be performed. The Facility operates on a partial cost-recovery system with investigators being charged on a per slide basis for all work. Per slide costs include diagnostic evaluation by a pathologist. A listing of the investigators who use the Facility in 1996-1997 is given below. The Histopathology Facility to date has made fundamental contributions to the research objectives of the AHFCC.